This invention relates to magnetic bubble domain chip packages and, more particularly, to a magnetic bubble domain chip package and a method of its mass assembly in which a coplanar relationship between the signal leads for the chip and the active surface of the chip is induced in order to insure more noise-free operation, and in which the chip is located in the most uniform part of the magnetic field used to drive the magnetic bubble domains thereon.
With the advancement of magnetic bubble domain technology, the need for a small, lightweight package which can be mass produced inexpensively has become paramount. Because of the special requirements and operating features of magnetic bubble domain chips, the packaging of these devices is a unique problem. Unlike semiconductors, magnetic bubble domain chips require two magnetic fields, a constant bias field perpendicular to the plane of the chip which keeps the bubble domains in a nonvolatile state, and a rotating magnetic drive field in the plane of the chip which controls the movement of bubble domains on the surface of the chip. The latter magnetic field presents the most difficult problem; the field is acquired by winding two coils in orthogonal relationship with respect to each other and then driving them with signals which are 90.degree. out of phase with each other. Placing the coils inside a conventional package presents a problem since the signal leads to the chip must be routed through the coils, thus increasing the size of the coils and, necessarily, the power required to drive them. Coils external to the package have even larger volume and the corresponding larger power requirements and, in addition, are physically awkward, resulting in a very large final package. Consequently, one object of this invention is to disclose a package which will allow a reduction in size of the drive field coils while keeping the coils internal to the package, thus decreasing the size and weight of the final package and the power required to operate it.
Traditional wire bonding methods used in the construction of magnetic bubble domain packages result in a package in which the signal leads are not coplanar with the active surface of the magnetic bubble domain chip. Furthermore, these wire bonds do not permit the drive coils to be prewound on a coil carrier member and inserted over the chip. In this bonding method, the chip, attached to a substrate material, is bonded to conductors disposed on the substrate material with "flying leads," which do not lie flat and thus have a vertical component in the plane of the drive field, producing noise. In addition these bonds are formed one at a time, thus increasing time and expense of manufacture. Thus another object of this invention is to demonstrate an automatic, high speed bonding technique which will both facilitate this type of production procedure and insure more noise free operation.
The use of the preformed insulating film, the high speed bonding technique, and a component coil carrier member in accordance with the present invention results in an improved magnetic bubble chip package readily leading itself to a mass production method which can be implemented easily and inexpensively.